I can't play my mp3's as my ringers

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Please help me! My ringtones I had setup as my ringers, mysteriously stopped playing. I can go to the song in whatever file it's placed at, but it won't play.
I downloaded smart explorer, and setup a mp3 extension, which now allows me to play the MP3's, but I still can't set them up as my ringers. It will be greatly appreciate for your help, as I refuse 2 reset....That'll be da last option